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The reaction of isatin with a base such as potassium hydroxide hydrolyses the amide bond to give the keto-acid 2. This intermediate can be isolated, but is typically not. A ketone (or aldehyde) will react with the aniline to give the imine (3) and the enamine (4). The enamine will cyclize and dehydrate to give the desired quinoline (5).
Examples of boronic esters Boronic ester Diol Structural formula Molar mass CAS number Boiling point (°C) Allylboronic acid pinacol ester: pinacol: 168.04: 72824-04-5: 50–53 (5 mmHg) Phenyl boronic acid trimethylene glycol ester: trimethylene glycol: 161.99: 4406-77-3: 106 (2 mm Hg) Diisopropoxymethylborane: isopropanol: 144.02 86595-27-9: ...
Pinacol is a branched alcohol which finds use in organic syntheses. It is a diol that has hydroxyl groups on vicinal carbon atoms. A white solid that melts just above room temperature, pinacol is notable for undergoing the pinacol rearrangement in the presence of acid and for being the namesake of the pinacol coupling reaction .
Basic heteroaromatic boronic acids (boronic acids that contain a basic nitrogen atom, such as 2-pyridine boronic acid) display additional protodeboronation mechanisms. [4] A key finding shows the speciation of basic heteroaromatic boronic acids to be analogous to that of simple amino acids , with zwitterionic species forming under neutral pH ...
It has the formula [(CH 3) 4 C 2 O 2 B] 2; the pinacol groups are sometimes abbreviated as "pin", so the structure is sometimes represented as B 2 pin 2. It is a colourless solid that is soluble in organic solvents. It is a commercially available reagent for making pinacol boronic esters for organic synthesis.
Pinacolborane also affects catalyst-free hydroboration of aldehydes, [5] ketones, [6] and carboxylic acids. [7] Pinacolborane is used in borylation, a form of C-H activation. [8] [9] Dehydrogenation of pinacolborane affords dipinacolatodiborane (B 2 pin 2): [10] 2 (CH 3) 4 C 2 O 2 BH → (CH 3) 4 C 2 O 2 B-BO 2 C 2 (CH 3) 4 + H 2
The pinacol reaction is extremely well-studied and tolerates many different reductants, including electrochemical syntheses.Variants are known for homo- and cross-coupling, intra- and inter-molecular reactions with appropriate diastereo- or enantioselectivity; [2] as of 2006, the only unsettled frontier was enantioselective cross-coupling of aliphatic aldehydes. [3]
The C–B bond of boronic acids and esters are slightly longer than typical C–C single bonds with a range of 1.55-1.59 Å. The lengthened C–B bond relative to the C–C bond results in a bond energy that is also slightly less than that of C–C bonds (323 kJ/mol for C–B vs 358 kJ/mol for C–C). [ 6 ]